二甲醚均质压燃、柴油补燃混合燃烧模式的试验研究

在一台4102直喷柴油机上研究了二甲醚（DME）均质压燃，柴油补燃混合燃烧模式对发动机性能、排放、油耗和燃烧特性的影响。试验结果表明，采用混合燃烧模式能有效降低发动机的碳烟排放及低负荷区域的NOx排放，但在整个工作区域内发动机的当量燃油耗偏高。此外，通过燃烧分析发现，大部分负荷下采用混合燃烧模式的发动机气缸最高燃烧压力比采用纯柴油的高，但最大压力升高率和压力升高加速度却比较低，因此发动机运行比较柔和。     

车用多缸直喷柴油机燃用二甲醚的燃烧和排放特性研究

开展了4缸直喷柴油机燃用二甲醚时的燃烧和排放特性的研究。结果表明，适当增加喷油器伸出缸盖底平面的距离，采用流通截面较大的喷油器，降低启喷压力，可以提高CA498发动机燃用二甲醚时的热效率。燃用二甲醚时，发动机缸内的最大爆发压力和压力升高率低于燃用柴油时的情况。二甲醚发动机在所有工况下均可实现无碳烟排放，NO，排放约为柴油机的50％，CO和HC排放与柴油机相当。试验结果表明二甲醚是一种高效、低排放、燃烧噪声低的柴油机新型代用燃料。     

直列泵柴油机燃用二甲醚(DME)的燃烧排放特性分析

在一台增压直列泵柴油机进行了燃用柴油和二甲醚的试验,实测了缸内压力,并据此计算了燃烧放热率,对动力性及排放特性进行了对比分析。结果表明:发动机燃用二甲醚后,功率和扭矩都有所提升,选用9°CA和12°CA供油提前角时,在不同转速下的NOx排放均低于柴油;在全负荷情况下的最高燃烧压力和峰值放热率均低于柴油;二甲醚的喷油量是柴油的两倍,但二甲醚的燃烧速度高于柴油,所以二者的燃烧持续期相差不大;选用6孔的喷嘴比5孔喷嘴燃烧更加充分,但是较高的最高燃烧压力和燃烧放热律也使得NOx排放增加。     

柴油机燃用二甲醚的燃烧特性

对直喷式柴油机燃用二甲醚的燃烧特性进行了研究,测量了示功图和油器针阀升程,计算了燃烧特性并与燃用柴油进行对比。结果表明,与柴油相比,发动机燃用二甲醚时的喷油延迟期延长,滞燃期缩短,最高爆发压力和最大压力升高率均低于柴油机。研究表明发动机燃用二甲醚具有良好燃烧特性。     

二甲醚发动机动力及排放性能研究

在一台车用单缸直喷柴油机上进行了燃用二甲醚的试验研究,结果表明:二甲醚发动机的动力性及排放性能优于柴油机.基于二甲醚燃烧数值仿真计算平台,建立氮氧化物模型.利用建立的平台计算二甲醚发动机在不同负荷下的动力及排放性能.得出:仿真结果与试验结果相同.研究结果表明:二甲醚发动机的NOx排放比柴油机大幅度降低,二甲醚发动机可以完全消除碳烟排放,二甲醚是一种可以替代柴油的理想清洁燃料.     

ZS195柴油机燃用二甲醚的试验研究

根据二甲醚燃料的特性,在ZS195柴油机上进行了供油量、供油提前角、喷油压力的参数优化和匹配,以及这些参数对柴油机燃用二甲醚的动力性影响进行试验研究。并对燃油供给系统低压部分进行改造,保证发动机的正常运转。试验结果表明：ZS195柴油机燃用二甲醚燃料在中、低速区动力性优于原柴油机。发动机全负荷范围内达到无烟排放,NOx有较大幅度下降,噪声有所减小,二甲醚燃料是一种可代替柴油的有前景的清洁燃烧。     

基于详细化学反应机理的增压二甲醚发动机燃烧与NO_x排放数值研究

使用KIVA-3V对增压柴油机和二甲醚发动机标定功率点的缸内燃烧过程与NOx排放进行了数值模拟研究.研究结果表明:计算所得的气缸压力和放热率曲线与实测值吻合较好.对缸内燃烧的温度分布计算表明:柴油燃烧滞燃期为2.5 °CA左右,二甲醚为1.5 °CA.柴油燃料着火始于喷雾前端两侧,在燃烧初期,其高温区分布在喷雾前端一侧,且在燃烧室内气流作用下沿垂直于喷雾方向扩散;二甲醚的着火点位于喷嘴附近,随喷雾的进行,其燃烧高温区从喷嘴附近一直延伸到喷雾前端,呈现狭长的高温带.在扩散燃烧后期,与柴油相比,二甲醚燃烧温度分布较均匀,且最高温度比柴油低.选用的9步NOx生成机理可较好地预测发动机实际运行中NOx排放水平.     

ZS195柴油机燃用二甲醚(DME)-柴油混合燃料的试验研究

二甲醚粘度低，会使高压供油系统产生泄漏及早期磨损。在二甲醚中添加低比例的柴油(简称二元燃料)，其柴油既参与燃烧，又相应提高了混合燃料的粘度。首先对二甲醚添加低比例的柴油进行优化并对柴油机供油量、供油提前角和针阀开启压力进行优化匹配，然后对ZS195柴油机燃用二元燃料进行试验研究。结果表明：在ZS195柴油机上燃用二元燃料，其功率和转矩略优于原柴油机，发动机在全负荷范围内接近无烟排放，NOχ大幅度下降。试验还表明，采用这种二元燃料可使供油系统长期稳定地工作。     

二甲醚发动机燃烧特性的试验与数值模拟研究

在一台直喷式压燃发动机上开展了二甲醚燃烧与排放特性的试验与数值模拟研究。测量了二甲醚在高压燃油泵内的泄漏量及其与发动机转速之间的定量关系,并就发动机分别燃用二甲醚和柴油的运转性能进行了对比试验研究,结果表明,发动机燃用二甲醚要比燃用柴油具有更好的性能与排放水平;另从二甲醚低温着火的化学反应机理人手,开展了其自燃着火过程的数值模拟研究,进而建立了计及温度、压力和燃空当量比因素的DME滞燃期数据库;通过将该数据库与发动机循环模拟程序相耦合,对DME发动机的运转性能进行了变参数预测分析,预测结果与试验结果吻合较好。     

直喷柴油机燃用二甲醚的试验研究

在直接喷射式柴油机上进行了燃用二甲醚的试验研究,对柱塞有效行程和柱塞直径、供油提前角、喷油压力、进气涡流比、喷嘴型式等燃烧系统主要参数对发动机功率和热效率的影响进行了研究,在燃料供给系统中增加燃油输送泵,消除了气阻,发动机可以在宽广的转速和负荷范围内稳定运行,发动机热效率比原机高３％ 。在优化燃烧系统参数的基础上对示功图和排放的测量及计算表明：二甲醚发动机最高爆发压力、最大压力升高率和 Ｎ Ｏｘ 排放均低于原机,烟度排放为０。试验结果显示了直喷式柴油机燃用二甲醚在降低排放方面的优越性能。     

Study of combustion and emission characteristics of turbocharged diesel engine fuelled with dimethylether

An experimental study of a turbocharged diesel engine operating on dimethyl ether (DME) was conducted. The combustion and emission characteristics of the DME engine were investigated. The results show that the maximum torque and power of DME are greater than those of diesel, particularly at low speeds; the brake specific fuel consumption of DME is lower than that of diesel at low and middle engine speeds, and the injection delay of DME is longer than that of diesel. However, the maximum cylinder pressure, maximum pressure rise rate and combustion noises of the DME engine are lower than those of diesel. The combustion velocity of DME is faster than that of diesel, resulting in a shorter combustion duration of DME. Compared with the diesel engine, NO_x emission of the DME engine is reduced by 41.6% on ESC data. In addition, the DME engine is smoke free at any operating condition.     

Study of combustion and emission characteristics of turbocharged diesel engine fuelled with dimethylether

An experimental study of a turbocharged diesel engine operating on dimethyl ether (DME) was conducted. The combustion and emission characteristics of the DME engine were investigated. The results show that the maximum torque and power of DME are greater than those of diesel, particularly at low speeds; the brake specific fuel consumption of DME is lower than that of diesel at low and middle engine speeds, and the injection delay of DME is longer than that of diesel. However, the maximum cylinder pressure, maximum pressure rise rate and combustion noises of the DME engine are lower than those of diesel. The combustion velocity of DME is faster than that of diesel, resulting in a shorter combustion duration of DME. Compared with the diesel engine, NO _x emission of the DME engine is reduced by 41.6% on ESC data. In addition, the DME engine is smoke free at any operating condition. __________ Translated from Transactions of CSICE, 2006, 24(3): 193–199 [译自: 内燃机学报]     

二甲基醚（DME）燃烧特性研究

作者在定容燃烧弹上用火焰直接成像法研究二甲基醚 (DME)燃烧过程 ,研究了 DME的滞燃期和火焰传播特性以及不同环境温度和压力对燃烧过程的影响。研究结果表明 ,DME的滞燃期比柴油短 ,燃烧室内的温度和压力升高时 ,滞燃期缩短 ;DME的着火位置靠近喷嘴一侧 ,柴油与 DME的体积相同时 ,DME的燃烧持续期比柴油短 ;DME的燃烧火焰亮度比柴油小 ,表明 DME的燃烧温度比柴油低。燃烧后期 ,燃用 DME时 ,喷嘴有明显的泄漏现象。此外 ,作者在单缸直喷式柴油机上进行了燃用 DME的燃烧特性试验研究 ,研究结果表明 ,DME的预混合燃烧放热率比柴油低 ,缸内最大爆发压力和最大压力升高率比柴油低。由于喷油持续期延长 ,DME的燃烧持续期比柴油长 ,在上止点后 80° CA出现一个较大的放热峰值。     

二甲基醚/天然气双燃料均质压燃的燃烧特性

应用零维热力学模型和化学反应动力学模型计算并分析了二甲基醚(DME)／天然气(CNG)双燃料均质压燃(HCCI)运行工况范围，计算与试验结果相吻合．采用DME／CNG双燃料方式可以有效地扩展HCCI的运行工况范围，发动机转速为1400r／min，最大平均有效压力可达O．52MPa．在一台单缸直喷式柴油机上进行了DME／CNG双燃料HCCI燃烧过程的试验研究，结果表明，DME／CNG双燃料燃烧过程表现出明显的两阶段放热过程，随着CNG浓度增大，缸内最大爆发压力增大，燃烧始点略有推迟，燃烧第二放热峰值增大．而DME浓度对燃烧过程的影响主要通过影响第一阶段放热过程，进而影响第二阶段放热，随着DME浓度加大，第一放热峰值增大，燃烧始点提前，导致第二放热峰值增大，缸内最大爆发压力增大，主燃期缩短，当DME浓度太高时，发动机将出现爆震．     

直喷式柴油机燃用二甲基醚(DME)试验研究

介绍了在1100单缸直喷式柴油机上燃用DME的发动机试验研究结果。研究表明：通过增加循环供油量可使柴油机燃用DME后恢复到原机略低，同时缸内最大爆发压力降低，发动机碳烟排放为零，HC和CO排放比原机略高，NOx排放比原柴油机降低约50%以上，供油提前角减少，缺内最大爆发压力降低，NOx排放可进一步大幅度降低，但HC排放略有升高；加大喷孔直径，缸内爆发压力升高，NOx排放升高，HC和CO排放在中低负荷相差不大，但在大负荷工况有所升高。     

Combustion performance and emission reduction characteristics of automotive DME engine system

This article is a condensed overview of a dimethyl ether (DME) fuel application for a compression ignition diesel engine. In this review article, the spray, atomization, combustion and exhaust emissions characteristics from a DME-fueled engine are described, as well as the fundamental fuel properties including the vapor pressure, kinematic viscosity, cetane number, and the bulk modulus. DME fuel exists as gas phase at atmospheric state and it must be pressurized to supply the liquid DME to fuel injection system. In addition, DME-fueled engine needs the modification of fuel supply and injection system because the low viscosity of DME caused the leakage. Different fuel properties such as low density, viscosity and higher vapor pressure compared to diesel fuel induced the shorter spray tip penetration, wider cone angle, and smaller droplet size than diesel fuel. The ignition of DME fuel in combustion chamber starts in advance compared to diesel or biodiesel fueled compression ignition engine due to higher cetane number than diesel and biodiesel fuels. In addition, DME combustion is soot-free since it has no carbon–carbon bonds, and has lower HC and CO emissions than that of diesel combustion. The NO_x emission from DME-fueled combustion can be reduced by the application of EGR (exhaust gas recirculation). This article also describes various technologies to reduce NO_x emission from DME-fueled engines, such as the multiple injection strategy and premixed combustion. Finally, the development trends of DME-fueled vehicle are described with various experimental results and discussion for fuel properties, spray atomization characteristics, combustion performance, and exhaust emissions characteristics of DME fuel.     

Analysis of energy release and NOx emissions of a CI engine fuelled on diesel and DME

Combustion and NO_x emissions from a dimethyl ether (DME) fuelled compression ignition engine were investigated. The test engine used consisted of an unmodified two-cylinder direct injection four-stroke air cooled type. The injection timing and injector opening pressure were left unaltered from their diesel fuelling settings. Analysis of the fuel line pressure shows that due to the compressibility of DME the rate of pressure rise was lower, resulting in injection occurring later when compared to diesel injection. The maximum combustion chamber pressure was found to be higher in the case of diesel fuelling. In terms of energy release it was found that with DME this occurs later than in the case of diesel fuelling with the larger proportion occurring just after top dead centre. A comparison of NO_x emissions revealed that, at all loads tested, these were higher in the case of DME fuelling and decreased steadily with increasing speed. At the higher speeds however, the levels of NO_x monitored were noted to be less than those of their diesel counterpart. Some of the factors influencing the promotion of NO_x emissions with DME fuelling are discussed and analysed.